Impulse control sensor system

ABSTRACT

The invention is an impulse control sensor system for a solid propellant powered rocket motor, said system utilizing a sensing deflagrating fuse responsive to the burning front of solid propellant, a thrust control means and a transducer means communicatively connecting said fuse and said thrust control means.

United States Patent 191 [111 3,815,358 Younkin June 11, 1974 [54] MPULSE CO SENSOR SYSTEM FORElGN PATENTS OR APPLICATIONS Inventor: Harry A. Younkin, Cumberland,

Assignee: Hercules Incorporated, Wilmington,

Del.

Filed: Sept. 25, 1972 Appl. No.: 292,228

US. Cl. 60/234, 60/254 Int. Cl. F02k 9/04 Field of Search 60/254, 234; l02/49.3,

References Cited UNITED STATES PATENTS 10/1972 Pelham et al. 60/254 X 723,040 2/1955 GreatBritain.. 60/254 Primary ExaminerCarlton R. Croyle Assistant Examiner-Robert E. Garrett Attorney, Agent, or FirmJames W. Peterson [5 7] ABSTRACT means and a transducer means communicatively connecting said fuseand said thrust control means.

7 Claims, 5 Drawing Figures PATENTEDJM 1 1 m4 .SHEEI 10F 2 FIG! FIG. 2

, I IMPULSE CONTROL SENSOR SYSTEM This invention relates to a simple impulse control sensor system for a solid propellant powered rocket motor in which a deflagrating fuse is employed as sensing element. In another aspect this invention relates to a process for controlling the impulse of a rocket motor employing a deflagrating fuse as an element for measuring the amount of propellant consumed.

I In the expanding applications of solid propellant rockets to meet the demands of sophisticated mission requirements deemed necessary of future space and defensive ballistic rocket systems, the need for providing precise control of impulse energy and auxiliary control systems is quite important. Many techniques and systems have been devised for terminating combustion, reversing thrust or changing the course of a rocket. However, few simple, low-cost techniques are available for sensing the energy level of a rocket motor and for providing a signal at a precise moment to effect control or actuation of an impulse control system.

Most impulse sensing techniques are based upon the principle'of either measuring motor combustion pres-. sure, rocket acceleration, or operating time, which are dependent upon sub-systems having sophisticated components, electronic circuits or computing systems. Such systems are costly, and have reliability, storage and operational problems resulting, in part, from the wide temperature extremes and environmental conditions in which such systems must operate.

Accordingly, it is the object of this invention to provide a simple sensing device which can be employed to operate an impulse control system in a solid propellant powered rocket motor at predetermined times which is low in cost, has good operating characteristics, long term storage capability over wide temperature extremes and environmental conditions and does not require electrical circuitry or components for reliable operation.

Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter. For a complete understanding of the nature and objects of this invention, reference is made to the following detailed description and drawings.

In accordance with this invention an impulse control sensor system is provided for solid propellant powered rocket motors comprising at least one sensing element containing a deflagrating fuse embedded in solid propellant contained within the rocket motor to be controlled. The sensing element is communicatively connected to a transducing means containing a deflagrating fuse which in turn is connected to an impulse control means such as a liquid quench system. The impulse control system is made operative upon receipt of a signal initiated by burning of the deflagrating fuse.

The impulse control sensor system of this invention is based simply upon the principle of correlating motor performance based upon known solid propellant rocket motor ballistics with the predetermined conditions at which it is desired to control thrust. Specifically, the percentage of propellant consumed in operation of the accordance with the following equation (1 W, 1, By correlating the weight of propellant consumed, W to the web distance burned, W a. desired impulse energy level for the rocket motor can be programmed be fore flight by locating a sensing element in the propellant at the web distance commensurate with the desired impulse increment. Web distance is the thickness of propellant measured normal to the burning surface. Thus, by embedding a sensing element within a propellant web at a web distance commensurate with the weight of propellant required to provide the desired impulse, a simple means of providing signals'for the acti vation of a thrust control system is provided without costly, sophisticated equipment. H

Multiple sensing elements and a switch to provide selection between the various sensing elements embedded at various depths in the propellant web can also be employed. A selector switch or safe arm switch is employed in the system to connect a selected sensing element to the impulse control device for operation at the predetermined condition during firing of the rocket motor.

The impulse control sensor system of this invention is more fully illustrated in the drawings which follow. In the drawings, like numbers refer to like parts where applicable.

FIG. I is a partial longitudinal view'partly in section illustratingan impulse control sensor system of this invention in which a deflagrating fuse is embedded directly into the solid propellent web of the rocket motor to function as a propellant burn distance sensing ele ment. I

FIG. 2 is an enlarged detail view of the sensing element of FIG. I.

FIG. 3 is a partial longitudinal view partly in section illustrating another embodiment of the thrust control system of this invention in which a selector switch is employed with multiple deflagrating fuse sensing elements embedded in a removable solid propellant charge inserted into the rocket motor.

FIG. 4 is an enlarged detailed view partly in section of the burning distance probe assembly of FIG. 3.

FIG. 5 is a detailed view along lines 5-5 of FIG. 4.

has two threaded bosses l4, l6. Sensing element 18 comprising'support rods 22, 24, a through bulkhead initiator 26, a donor charge 28, a receiving charge 30 and a deflagrating fuse 32 contained within cavities 34,

36 within each support rod 22, 24 are threadably secured within bosses l4, l6 and sealed by O-rings such as 14a. Donor charge 28 is secured at the base of support rod 22 within through bulkhead initiator 26 and is contiguous with deflagrating fuse 3.2. Receiving charge 30 is positioned at the base of support rod 24 within rocket motor is correlated to time, energy level or flight characteristic through known ballistic characteristics ofthe rocket motor. For example. the total impulse energy I of a rocket motor can be expressed as the product of (a) the weight of propellant consumed W and (b) the specific impulse energy of the propellant, I in through bulkhead initiator 26 and is contiguous with deflagrating fuse 33. Through bulkhead initiator 26 has two partial longitudinal cavities 38, 40 in axial alignpositioned at an angle of 90 with the longitudinal axis 46 of the rocket motor case It). In the embodiment shown, the support tubes 22 and 24 are positioned normal to the propellant burning surface 48. Support tube 24 is coupled to sensor transfer line 50, which is a combustion resistant tubular casing containing a deflagrating fuse 52. Sensor transfer line 50 is in turn connected to selector switch 54. Selector switch 54 can be designed to have several operative positions which can be preselected in conjunction with one of several burn distance sensing elements 18, 20. The selector switch is connected through a signal transfer line 56 to an impulse control system such as a liquid quench system 58. Signal transfer line 56 is of like construction to transfer line 50.

OPERATION OF THE TI-IRUST CONTROL SYSTEM The operation of the thrust control system is as follows. Prior to firing of the rocket motor the selector switch is preset for thrust termination to occur when a predetermined amount of propellant has been consumed. After the rocket motor is fired, the propellant l2 burns perpendicularly to the propellant surface 48 until the burning surface reaches support rod 22 containing deflagrating composition 32. Deflagrating fuse 32 burns at a very high rate, but generally below the rate of sound transmissiomand initiates explosion of donor charge 28. The shock wave resulting from explosion of donor charge 28 passes through diaphragm 42 and initiates explosion of receiving charge 30 which in turn initiates the deflagrating fuse 33 in support rod 24 and in turn the deflagrating fuse 52 in transfer line 50. Selector switch 54 ispositioned selective to sensing element 18, and a deflagration is transmitted through line 56 to the initiator of the impulse control system 58, where the deflagrating burning front ignites the liquid quench pyrotechnic pressurizating charge (not shown) causing activation of the quench system. Ignition of the charge can be either directly by the deflagrating fuse or through a thin bulkhead initiator with a pyrotechnic output. Burning of the propellant I2 is terminated by the quench system 58 thereby terminating motor combustion and impulse. It is to be understood that the sequence of events from initiation of the deflagrating fuse 32 in support rod 22 until initiation of the impulse con trol system 58, takes place in from about 0.5 to 3 milliseconds.

In FIGS, 3 and 4 a second embodiment of the impulse control sensor system of this invention is illustrated. A burn distance probe sensing assembly 64 is shown inserted into a cavity 60 which extends through rocket motor case 61 and into propellant charge 62. The cavity in the rocket motor case 61 and the propellant charge 62 are in registering relationship. A burn distance sensing probe assembly 64 is inserted into cavity 60. The burn distance sensing probe assembly 64 consists of an aluminum closure head 66 and a phenolic cylinder 68 which is secured to peripheral surface 70 of the interior face 72 of closure head 66. The sensing probe assembly 64 is in the form of a cylinder which is closed at one endby closure head 66. A propellant charge 73 is secured in the open end of the cylinder.

Closure head 66' has a series of cylindrical cavities 74,

76 extending through closure head 66. The cavities 74, 76 are spaced an equal distance from the center of the closure head, said cavities being symmetrically spaced axis of the closure head 66. Two sensing elements 86,

82 prepared from phenolic rods are bonded to the walls formed by the cavities 74, 76 in the forward end of closure head 66. A deflagrating fuse 84 is held within each cavity 86, 88 which extends throughout the length of each element 86, 82 respectively.

The selector switch 90 shown illustrates the selection principle and is only one of many configurations which can be employed to provide selection between sensing elements. The selector switch 90 consists of an aluminum body 92 having a cavity 94 therethrough. Cavity 94 contains a deflagrating fuse 96 and a connecting means 98 for connecting deflagrating fuse 96 to a deflagrating fuse transfer line 99 which is in turn connected to the impulse control system to be activated. Selector switch body 92 has a conical forward surface I06. Selector switch body 92 is slidably receivable into the aftend ofclosure head 66. A rubber gasket 102 is bonded to forward surface 100 of selector switch 99. The selector switch body 92 is retained and maintained in a selected position by means of a compression spring 104, an aluminum plate closure 106, and detent pins 108. Rubber O-rings M6 and rubber gasket 1102 are provided as shown in the assembly to provide pressure seals and prevent gas leakage when the selector switch is positioned operative to a sensing element as shown in FIG. 4. In the operative position the entire deflagrating fuse train 84, 96, 99 is in a communicating relationship for the selected sensing element position 80.

The selector switch assembly shown provides for five positions, one position for each of the four sensing elements and a null position employed when activation of the transfer circuit is not desired. Positioning is provided by pulling the body 92 of switch 90 against spring 1041 and rotating the switch body 92 to the desired position, which position is then maintained by means of compression springs I04, detent pins 198 in switch body 92 and receptacle holes 109 in probe closure head 66 as shown in FIGS. 4 and 5. Two detent pins for each location are used to facilitate easy operation and maintain alignment of the plunger body 92. Coincident with the detent pin location for each sensing element is a marking on the closure 66 which is visible and labeled. The selected sensing element to be operative is aligned with a mark on plunger body 92 such that the sensing element position selected can visually be deter mined from the position of the selector switch.

Prior to rocket motor ignition the desired sensor location is selected and continuity between the sensing element and the impulse control device quench system) to be activated is accomplished by rotating the selector switch 92 to align the deflagrating fuse 96 within the cavity in the selector switch 90 with the deflagrating composition 86 in sensing element 80. Selector switch 90 is in operative relationship to sensing element and locked in operative position with detent pins 108. As an additional feature to maintain the selector switch in the selected position and also provide added safety to ensure sealing of all the'other sensors not selected, motor pressure is allowed to bleed from the pressurized rocket motor chamber through port 112 to pressurize cavity 114 defined between closure plate 106 and selector switch body 92 causing additional force'to be applied to the switch body 92 and gasket 102 to effect positive sealing.

5 The impulse con l sensor y I em heretofore desgf gs 870 5 l-5 emp oys com tron of a defla Bum-mg (mm 5% U3 m ch nicalf atures in the system an Avg. c xrt com y w on e\ecn.ica\ Sensor web distance location. .90l7 .2\

r 'nche (m asured from ori inal les further illustrate the impulse 5 f y g r system and operational principles of this w S m 1* TPC Web burned (inches) .9077 ()1 (.27)" I (mgasured from origin' su ace charge) EXAMPLES integral of pressure-time I Pdt 15053 53 (.28\*

. sia-sec e e conducted at F. conditions to to Tgmumpuge vaflmon 53 L34 ntally verify the operationa rinciples of l (l W,, i based upon data a l '-se r robe and atest a arag 3 P nia bu 2 8 p p m test *Based upon results from two tests 7 e g f zfsg 8; im fiigxi The foregoing tests show unifor web burning beb Y d 6 10 oumd char 6 tween the probe charges an TlC propellant grain wi i e C moyto zp coma) no measurable difference in burning rate he differe'assembw attache 5 meted to a p ence between the se or ice tron web conpamms h mdudes base jam a POW sumed can be attributed to the time b d e to the test 6 mate a a 5 eat 5 he mut- Sensor set u and accuracy wi which th ried propellant S of awphmm-c cup ssgmbw w two surface can easure Activation of the propellant ma of stran of 0.040-inch diameeject-9n and quench S m Yap. h sheamad pymmch deflagrm-mg {use milliseconds lapsing from ignition f t eflagrating Cm w 3 man a composition u til s ear disc failure results There is, 7 Compmksdp b mo O mc howev r, ti e bias between the ti the shear disc h nolic rods a d p aced t the several differ amd the t n? Wale stances meas g from he f m 0 which adds error a d ration in dat The coeffi charge 0 6 pr 6 m ch 3 cient of variation C,.) in burn we d tance e hamctemed bamsdcany is ca t amun creases as th d tance to sensor location is in and b fi 0 pom creased, therefore, e a cura thei pulse con 0 TPC) gr ins are c st in acyl dric lcontigura Sens Y5 f Went can P propel m havmg the same c mposmon as rocket mot ha mg large pr ell nt web thickness that employed i th multi-sen p h e welgh l p fi? med these tests (g me mu d 0 t 6 outs e d ametet correlatable othe propellant eb distance burne an have a 4 5-inch out de diamete l 8 i bummg Ge 6 ameter cente po m h g 1 weight pressed as th duct of th weight of p opellant con ounds. All the test e set for termination at s umed and the propellant specific ll'll T st result inch web distan e fr h pr ll nt rf Q h in mate the coeffici t of ariation in m ulse sensm multi-sensor r be char to be it ected mpl y g e burn d stance sensin P g Operation test co of simultaneous m. 0 system of this inven 10 w be from to 0.6

t o d Wh lclaim an d sir o prote b tters Pate r a solid p out se e t at wh' me th deflagrating f e c p0 is 1g ed. Th ellant powe fuse bu mg fr nt is sf rred through transfer sensi g eans dd d in pr pellant within 5 acer, ntaining d fl grating co ositi of the id ropellan powered ro m r to bec same typ o the te f xture po der har e The tes trolled, said s using means 0 sing at least fixture p der charg by e burning e sensing defla rating use, said se sing mean compost causing c0 fr urning f p w s ortdi'ng substan 'al contac f said sei charge Mid l'll pressur devel Th high me 5 wr burn ng fro t 0 solid prop: ressure results i hea g f he shear di allowing wrthyn h rocket mg n the P 9 6 b e Comm 2 he P impulse contr me connect d to the r a d the molol' b e m C case motor o.c trol h thrust an i pulse 1 and dumped into ta '1 water n hed. Th rocket motor, a Yecovefed distance Sells 29 glam transducer mea unicative y connect are evalu d for burning rat ffec d the ability 0 Sew-mg a t S d \mvuse comm mean the sensing sy m to ac vate ue of the propellant mate 5a 186 comm means in Yes? redeter d times based 0 known ballistic (ms-mg of he bum-mg from of Sop-d props elfofma 2. A sensor 5 e as defined in claim 1 W et The resul f these tests ar ummarized in Table l Sensm efla mm d-ecfly solid propellant pow the rocket motor tc TABLE A d i d l 2. h sensor sy as e ine incaim w l PARTAL BURN TEST SUMMARY transducer mean comprises: Number T sts a donor explosive charge in contact with sa Propellant, type Composite means' Conditioning Temperature. "F. '7 from surface of .90 a receiver 8X \OSWC charge,

Sensor Position d re- Ise control mg? WWW STATES PATENT oiFlcE EERTIFICAEE OE CGBRECTION 33mm; Jun 11,, 1974 Patent H InventoriIss) Harry A. Youmkin (Casel it is aertifiied that error appears in the above-identified patent and that: maid wamm Mazemt ma'hamhy cwmreacted am shown below:

' olw 4, Line 52 of pap.

"dievice quench shtjuld. read device quench. o

Signed and saalwd this 19th day of Newembr 1974.

MCCOY M. miawm JR. (2. MARSHALL DANN Attesting Uffieer v Commissioner of Patents 

1. An impulse control sensor system for a solid propellant powered rocket motor, comprising: sensing means embedded in propellant within the solid propellant powered rocket motor to be controlled, said sensing means comprising at least one sensing deflagrating fuse, said sensing means responding to substantial contact of said sensing means with a burning front of solid propellant within the rocket motor; impulse control means connected to the rocket motor to control the thrust and impulse of the rocket motor; and, transducer means communicatively connecting said sensing means to said impulse control means to activate said impulse control means in response to sensing of the burning front of solid propellant.
 2. A sensor system as defined in claim 1 wherein said sensing deflagrating fuse is embedded directly into the solid propellant powering the rocket motor to be controlled.
 3. A sensor system as defined in claim 2 wherein said transducer means comprises: a donor explosive charge in contact with said sensing means; a receiver explosive charge; a transducer deflagrating fuse connecting said receiver explosive charge and said impulse control means; and, diaphragm means separating said donor explosive charge and said receiver explosive charge, said donor charge being detonated by the sensing element, producing a shock front, said shock front initiating detonation of the receiving charge, initiating burning of the transducer deflagrating fuse to activate said impulse control means.
 4. A sensor system as defined in claim 3 wherein said impulse control means is a liquid quench system, comprising a liquid quench reservoir containing a liquid quench and pressurization means which is responsive to the burning of the transducer deflagrating fuse for activation and transferring the liquid quench from the reservoir to the interior of the rocket motor.
 5. A sensor system as defined in claim 1 wherein said sensing means includes a plurality of sensing deflagrating fuses and is embedded in solid propellant contained within a sensing assembly which is inserted into a cavity provided within the motor casing of the rocket motor being controlled.
 6. A sensor system as defined in claim 5 wherein said transducer means includes a selector switch containing a transducer deflagrating fuse, said selector switch providing for communicative connection of said impulse control means with a desired sensing deflagrating fuse or for rendering said transducer deflagrating fuse inoperative with undesired sensing deflagrating fuses.
 7. A sensor system as defined in claim 6 wherein said impulse control means is a liquid quench system, comprising a liquid quench reservoir containing a liquid quench and pressurization means which is responsive to the burning of the transducer deflagrating fuse for activation and transferring the liquid quench from the reservoir to the interior of the rocket motor. 